True to an extent, as I've asked myself countless times, 'why do US presidential aspirants campaign with things that doesn't directly improve the general well-being of the Americans?'

However, I think your research needs further researching regarding the internal policies and decision making of the US government. So far, I've never seen any government in the world that is as committed as the US government in securing the lives of its citizens and delivering promises made, I stand to be corrected though. Do your research, you'll observe that Russia and China that you just mentioned earlier are also grossly involved in external matters as the US, for instance, Russia's involvement in Africa and other parts of the world. China trying to intimidate the people of Taiwan, the US resistant move is what is placing them on the  light.

The takehome is, US is as involved in external matters as it is with the internal matters.